There are currently in the marketplace two types of traditional heat-sealed vinyl binders. One consists of a three-piece board construction that is welded together wherein a plastic material surrounds the three separate pieces and the hinges are formed by the plastic coverings being welded together between the spine and the front and back covers. The welded construction of this type of binder results in relatively weak hinge constructions that tend to fail with the covers pulling away from the spine. In the other traditional type, there is some connectivity or webbing taking place with the board, either the board has been slotted in the hinge areas, or it has been routed in the hinge areas, or the three pieces of board have been joined with a flexible backing. See the prior art illustrated in FIGS. 1A-D. In any case, the hinge areas are still substantially weak resulting in the covers severing from the spine. Examples of these board segmented constructions are illustrated in U.S. Pat. Nos. 5,222,825 and 5,620,207.
Another type of binder construction that has been employed is disclosed in British Patent 1,123,779. This patent discloses a binder in which a board is covered by plastic sheets that are welded to the board. However, it was found necessary to compromise the board by forming a cut-out portion at each end of a fold and thus reduces the strength of the board at the fold lines which obviously weakens the binder in these areas. There is also no teaching of providing a generally arcuate spine arrangement that is not weakened at any section thereof.
It can be appreciated that the aforementioned constructions have a number of inherent disadvantages that if overcome would be a substantial advance in the art and serve a long felt need to provide a binder with a much longer shelf life than is currently available. With the current construction the areas where the spine of the conventional binder hinges with the front and back covers have been substantially weakened by the welding in the hinge area. For example, in welding two pieces of 0.015 gauge thermoplastic material, the resultant thickness is not the expected 0.030 gauge but is approximately 0.020 gauge or less. The welding process forces the flexible plasticizers away from the welded area because pressure is used to create a bond and inevitably there is always a decrease in plasticizers and a resultant loss in dimensional stability in any welded area.
Additionally when the binder is fully loaded with paper, there are additional stresses placed on the covers of the binder. These stresses are transferred to the area of weakness found in the hinges which further acts to rapidly deteriorate the binder thus substantially reducing its longevity.
Of primary concern is that in the conventional binder the material forming the binder has been drastically compromised by milling, routing or slotting to facilitate the formation of the hinges which brings about the weaknesses above referred to. In addition this compromising of the board strength not only increases the likelihood of hinge failure and cover separation but it can also create a wobbling effect that does not allow the binders to stand up on their own when loaded with paper.
Another disadvantage of current binder constructions that need correcting is the ability to permit the binder producer to not have to predetermine what configuration the binder construction is to be ultimately fashioned until specific orders are received. This is not possible with currently available types since the milling, routing or slotting referred to must be done before the plastic sheets forming the final binder are secured to the underlying board via the heat sealing process, and are also predetermined by the tooling used to heat seal the plastic sheets around the board. It would be a substantial advantage to have the sandwich of board and surrounding plastic sheets stacked and available to be formed into any desired configuration (i.e. round back, flat back etc.) and the instant invention would allow the configuration to be determined after the final casing has been constructed, thus reducing inventory and lead times.
Also, under current practice the final construction for the capacity of the ring metal must be selected prior to welding the film to the board since the size and shape of the binder are predetermined because of the tooling and board specifications.
It remains to mention that the current manufacturing steps being employed as disclosed in U.S. Pat. No. 5,620,207 result in protuberances that are large and unsightly if not dealt with. These are often overcome by notching the board which further weakens the binder by reducing the amount of material at critical junctures or by welding a notch to hide the protuberences which changes the dimensional stability of the plastic covering and weakens it.
It can be appreciated that it would be desirable to have a one piece uniformly strong binder in which the rigid thickness of the cover continues throughout the hinge and is unable to rip or separate. Such a binder would not compromise the board nor have relatively weak hinge lines nor create protuberances or alter the virgin raw materials in the critical failure and stress areas of the hinge. The binder should be capable of using a vinyl or other suitable plastic covering that can be welded and/or glued and/or stitched around the underlying one-piece board. It would be a substantial advance in the art if the binder would have a seamless configuration and include a creased hinge construction that is the same thickness throughout the board and thus does not define a weakened hinge area yet provides a high degree of flexibility that will vary with the number of creases formed.
Also, it would be advantageous to have a binder that is versatile, that can have either a round or a flat spine and can also be changed in size. This can be especially appreciated in manufacturing because of fewer parts, simplification in tooling, and more efficient production procedures.
There has also been a need to provide a vinyl or other plastic covering for the binder that will not delaminate or split and be able to receive a clear plastic overlay to hold information. The clear plastic overlay differs from prior art in that it can extend from the front cover to the back cover and spine without interruption and can be made flat or round after the fact. To facilitate the manufacturing of a binder that overcomes the disadvantages of the prior art the heretofore relatively archaic process used to form binders is not suitable and a new process for manufacturing binders is required.
It is also desirable to be able to provide the inner plastic covering of the binder with partial plastic sheets adhered thereto on three sides to provide pockets into which various materials can be placed.